The present invention relates to an exposure apparatus for projecting and transferring the pattern of a master such as a mask onto a member such as a wafer coated with a photosensitive agent via a projection optical system.
A conventional manufacturing process for a semiconductor element such as an LSI or VLSI formed from a micropattern uses a reduction type projection exposure apparatus for printing by reduction projection a circuit pattern drawn on a mask onto a substrate coated with a photosensitive agent. With an increase in the packing density of semiconductor elements, demands have arisen for further micropatterning. Exposure apparatuses are coping with micropatterning along with the development of a resist process.
Methods of increasing the resolving power of the exposure apparatus include a method of changing the exposure wavelength to a shorter one, and a method of increasing the numerical aperture (NA) of the projection optical system.
As for the exposure wavelength, a KrF excimer laser with an oscillation wavelength of 365-nm i-line to recently 248 nm, and an ArF excimer laser with an oscillation wavelength around 193 nm have been developed. A fluorine (F2) excimer laser with an oscillation wavelength around 157 nm is also under development.
An ArF excimer laser with a wavelength around ultraviolet rays, particularly, 193 nm, and a fluorine (F2) excimer laser with an oscillation wavelength around 157 nm are known to have an oxygen (O2) absorption band around their wavelength band.
For example, a fluorine excimer laser has been applied to an exposure apparatus because of a short wavelength of 157 nm. The 157-nm wavelength falls within a wavelength region generally called a vacuum ultraviolet region. Light in this wavelength region is greatly absorbed by oxygen molecules. Light hardly passes through the air. Thus, the fluorine excimer laser can only be applied in a low-oxygen-concentration environment. According to xe2x80x9cPhotochemistry of Small Moleculesxe2x80x9d (Hideo Okabe, A Wiley-Interscience Publication, 1978, page 178), the absorption coefficient of oxygen to 167-nm light passes through a gas at an oxygen concentration of 1% at one atmospheric pressure, the transmittance per cm is only
T=exp(xe2x88x92190xc3x971 cmxc3x970.01 atm)=0.150.
Oxygen absorbs light to generate ozone, and the ozone promotes absorption of light, greatly decreasing the transmittance. In addition, various products generated by ozone are deposited on the surface of an optical element, decreasing the efficiency of the optical system.
To prevent this, the oxygen concentration in the optical path is suppressed to a low level of several ppm order or less by a purge means using inert gas such as nitrogen in the optical path of the exposure optical system of a projection exposure apparatus using a far ultraviolet laser such as an ArF excimer laser or fluorine (F2) excimer laser as a light source.
In such an exposure apparatus using an ArF excimer laser with a wavelength around ultraviolet rays, particularly, 193 nm, or a fluorine (F2) excimer laser with a wavelength around 157 nm, an ArF excimer laser beam or fluorine (F2) excimer laser beam is readily absorbed by a substance such as oxygen. Oxygen in the optical path must be purged to an oxygen concentration of several ppm order or less. This also applies to moisture, which must be removed to the ppm order or less.
It is an object of the present invention to provide an exposure apparatus for strictly removing an exposure obstacle such as oxygen or moisture in an exposure optical path, and performing stable exposure.
To achieve the above object, according to the present invention, there is provided an exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage and has a surface almost flush with a surface of the substrate, wherein a gap is formed between a side surface of the substrate and the top plate, and a depth of the gap is equal to or larger than a width of the gap.
A side surface of the chuck preferably has an inclined surface not perpendicular to the surface of the substrate. A side surface of a step between the surface of the top plate, and a bottom of the gap between the side surface of the substrate and the top plate preferably has an inclined surface not perpendicular to the surface of the substrate. A depth of the gap is preferably 1 mm or more from the surface of the substrate. A difference between the surface of the substrate and the surface of the top plate is preferably 4 mm or less.
To achieve the above object, according to the present invention, there is provided another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage and has a surface almost flush with a substrate support surface of the chuck.
It is preferable to form a gap between a side surface of the chuck and the top plate, and to form a vent hole which is larger in volume than the gap and communicates with the gap. A width between a side surface of the chuck and the top plate is preferably smaller than a width between the side surface of the chuck and an inner surface of the top plate. The exposure apparatus preferably further comprises a supply port for supplying gas into the gap formed between a side surface of the chuck and the top plate. The exposure apparatus preferably further comprises a vent hole which makes the gap formed between a side surface of the chuck and the top plate communicate with the surface of the top plate. The exposure apparatus preferably further comprises a vent hole which makes the gap formed between a side surface of the chuck and the top plate communicate with an opening formed in a surface almost parallel to a scan direction of the stage. An angle defined by the surface having the opening and the scan direction is preferably 30xc2x0 or less. A side surface of the chuck preferably has an inclined surface not perpendicular to a surface of the substrate. A difference in level between the substrate support surface of the chuck and the surface of the top plate is preferably 3 mm or less.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage and has a surface almost flush with a chuck support surface.
A difference in level between the chuck support surface of the stage and the surface of the top plate is preferably 2 mm or less.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage and forms a surface almost flush with a surface of the substrate, wherein a gap is formed between a side surface of the substrate and the top plate, and a vent hole, which is larger in volume than the gap and communicated with the gap is formed.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage and forms a surface almost flush with a surface of the substrate, wherein a gap between a side surface of the substrate and the surface of the top plate is smaller in width than a gap between a side surface of the chuck and the top plate.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, a top plate which is mounted on the stage and forms a surface almost flush with a surface of the substrate, and a supply port for supplying gas into a gap formed between a side surface of the substrate and the top plate.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, a top plate which is mounted on the stage and forms a surface almost flush with a surface of the substrate, and a vent hole which makes a gap between a side surface of the substrate and the top plate communicate with the surface of the top plate.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, a top plate which is mounted on the stage and forms a surface almost flush with a surface of the substrate, and a vent hole which makes a gap between a side surface of the substrate and the top plate communicate with an opening perpendicular to a plane almost parallel to a scan direction of the stage.
A side surface of a step formed by the surface of the top plate, and a bottom of a gap between a side surface of the substrate and the top plate preferably has an inclined surface not perpendicular to a surface of the substrate. A difference between a surface of the substrate and the surface of the top plate is preferably 4 mm or less.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage to hold the chuck, wherein a side surface of the chuck has an inclined surface.
To achieve the above object, according to the present invention, there is provided still another exposure apparatus comprising a chuck for holding a substrate, a stage for moving the chuck to align the substrate, a mechanism for purging an exposure optical path near the stage with inert gas, and a top plate which is mounted on the stage to hold the chuck, wherein a side surface of a step formed on the top plate has an inclined surface.
The purge mechanism preferably has a cover for covering an exposure optical path from a substrate-side lower end of a projection or illumination optical system to a vicinity of the stage, and a supply port for supplying inert gas into the cover. The supply port preferably includes at least one nozzle. The supply port preferably serves as the cover. It is preferable that one inner surface of the cover has a supply port for supplying purge gas, and the other of the cover has a recovery port for discharging purge gas. The cover preferably includes an air curtain formed from inert gas. The inert gas preferably includes any one of nitrogen, helium, and argon.
The top plate is preferably integrated with the stage.
The exposure light preferably includes ultraviolet rays. The ultraviolet rays preferably include a laser beam from a laser serving as a light source. The laser preferably includes a fluorine or an ArF excimer laser.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.